While child mortality rates have plummeted worldwide, nearly one-third of all children under 5 in developing countries are stunted. Children who are stunted (having low height-for-age) suffer from a long-term failure to grow, reflecting the cumulative effects of chronic deficits in food intake, poor care practices, and illness. The early years of life, especially the first 1,000 days, are critical; if a child’s growth is stunted during this period, the effects are irreversible and have lifelong and intergenerational consequences on their future human capital and potential to succeed.

For the water and sanitation community the year 2009 marked a turning point in our understanding of the role that Water, Sanitation and Hygiene (WASH) has on child stunting. A provocative Lancet article (Humphrey 2009) put forth the hypothesis that a key cause of child stunting is asymptomatic gut infection caused by ingestion of fecal bacteria. Small children living in poor sanitary environments are especially at risk, through frequent mouthing of fingers and objects during exploratory play, playing in areas contaminated with human and animal feces and ingesting contaminated food and water (Ngure et al. 2013). Researchers now estimate that up to 43 percent of stunting may be due to these gut infections, known as environmental enteric dysfunction (EED) (Guerrant et al. 2013).

Just last week estimates were released suggesting that poor sanitation is the second leading cause of child stunting worldwide (Danaei et al. 2016). In a key departure from previous work, the researchers defined risk as the sanitation level of a community, rather than an individual. This is consistent with mounting evidence showing that a community’s coverage of sanitation is more important than any one household’s (Andres et al. 2013). Across different studies, data sets and outcomes the evidence consistently shows that a threshold of around 60–70 percent household usage within a community is needed before the health and nutrition benefits of sanitation begin to accrue. Studies that have focused on an individual’s toilet use as a predictor, rather than a community’s use, may have vastly underestimated the impacts (Hunter and Prüss-Ustün 2016).

As we advance our understanding of the ways in which a poor sanitary environment impacts growth in small children, we can better design water and sanitation interventions to target these pathways. While there is a role for multi-sectoral interventions, which can simultaneously target the underlying determinants of child undernutrition, such as food security, access to health services, and childcare practices — there are ways that the water sector can adapt its own approaches so that they are more nutrition-sensitive, and more impactful on nutrition. Here are four key actions: